Waste not, want not! It’s a maxim that many manufacturers have been taking to heart in increasingly innovative ways these days. Take the Varo pulp mill operated by Sodra Cell near Varberg, Sweden. Rather than throwing unusable branches, bark and other remnants onto a trash heap, the paper manufacturer has invested in automation for transforming this waste into clean streams of revenue. Not only is the plant now more efficient and profitable, but fossil fuels also no longer fire the boilers that drive its pulp and power production.

Because making pulp requires a lot of steam, many producers, especially those in Scandinavia, divert some of the steam to generating their own electricity. So, besides making enough electricity to produce 425,000 tons of pulp a year, the Varo mill also generates 550 GW-h of surplus energy in the forms of electricity, steam and biofuels. The mill then sells 100 GW-h of its surplus to the national power grid and 150 GW-h of it as heating steam to homes in nearby Varberg, a town of 27,000. The remaining 300 GW-h goes to market as biofuels for power plants and industrial users.

As Sodra Cell and others in a variety of industries are discovering, automation can solve some of the problems that have made alternative energy sources too impractical and unprofitable in the past. For this reason, some businesses are turning to these solutions to deal with the rising cost of fossil fuels, the nagging uncertainty in the global economy, and growing concern for the environment.

Optimizing operations
At the Varo pulp mill, the key was the high level of integration permitted by Extended Automation System 800xA from ABB Inc.’s Process Automation Div. in Wickliffe, Ohio. Approximately 40 controllers oversee some 23,000 input/output (I/O) signals from 56 operator stations and optimize the processes. “The systems are connected in a common interface, which enables us to control what is happening in the various parts of our operations,” says Ola Walin, Varo’s maintenance manager.

Maintaining optimal settings is no small feat. “Often with alternative fuels, you don’t know exactly what their quality will be,” explains Marc Leroux, ABB’s marketing manager for collaborative production management. “Some of the bark and other remnants from trees might still be green, for example, which produces less usable heat.” To accommodate this and other sources of variation not normally found in refined fossil fuels, Varo’s control system needed the ability to adjust set points and other operating parameters automatically.

Leroux attributes this flexibility to two kinds of technical advancements. First is the ever-expanding computing power in each successive generation of control systems. “It gives you the ability to process the variables that you’re adding to your equations,” he says. “You also have more access to information for decision-making and a flexible way for creating the necessary models.”

The second advancement is the development of increasingly more sophisticated integrated advanced control software that sits on top of the control system for making decisions. At Sodra Cell’s Varo mill, such software monitors input fuel and its burning characteristics, matches it against the desired output, and either modifies the affected operating parameters or recommends adjustments to an operator. Other software manages the quantity and sale of the excess power.

>> Click here to read about Simulating Complex Processes for Alternative Energy Production.  

Nimble power plant
For similar reasons, load-following software also plays an important role in integrating wind and solar power into the power grid. “When a cloud comes overhead or the wind stops blowing, you’ve got to turn to fossil fuels, ramping up generation [at fossil-fired plants] to make up the loss in order to meet the demand,” explains Gary Woodward, director of business development at Emerson Process Management Power and Water Solutions Inc. of Pittsburgh.

The Minnkota Power Cooperative Inc. ran into this very problem at its Milton R. Young Station Unit 1 near Center, N.D. Once it joined a regional grid spanning 12 states and one Canadian province, the unit was called upon to compensate for the daily variations caused by changing winds at the participating 100-MW wind farm. “The plant didn’t get any advance information,” notes Woodward. “When the voltage started dropping, it had to try to respond instantly to make up the loss.”

Before joining the regional grid managed by the Midwest Independent Transmission System Operator Inc. based in Carmel, Ind., the coal-fired plant had a fairly predictable demand for power from the more than 110,000 customers who constituted its primary customer base. It would ramp up in ...